How to disable a recommended image field

Hi,

I have an image field which is recommended by default and set as signatory image as fall back for an digital signature.

When the digital signature is added the signatory image (for placing a scanned image) need to be disabled when I want to submit this.

Is there a script for.

I have now set the script to on presubmit event:

if (Surv-Submit.SignatureDigital.isNull) {
        this.mandatory = "warning";   
    }else{
        this.mandatory = "disabled";
    }

Anyone has a clue?It will be helpfull.

Regards,

Ed Boon